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Re: AS-REP

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On Thu, Mar 6, 2025 at 10:26 PM Jim Shi via Kerberos <kerberos@mit.edu>
wrote:

> Hi, is there easy way to check if AS-REP is valid or not?that is, is there
> is tool or stand alone program to check?
>

I don't know about an existing tool but in theory an AS-REP is pretty
self-contained which makes it "easy" relatively speaking. You just need the
base key (like from a keytab) to decrypt it and thus validate it.

But you would need a kerberos lib to help because it needs to generate a
so-called DK key or derived key which is a non-trivial bit of code. Meaning
it's not as simple as running it through AES-whatever.

There is a nonce generated in the AS-REQ that's supposed to be checked but
if you're just validating an AS-REQ I think it would be ok to ignore it
since it's primary purpose is to mix-up the ciphertext so that the KDC can
detect a replay and you're not a KDC.

Knowing this, in theory you could probably make a tool in a 100 lines of
python assuming there's a decent python kerberos lib out there.

Mike

-- 
Michael B Allen
Java AD DS Integration
https://www.ioplex.com/ <http://www.ioplex.com/>

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Re: AS-REP Michael B Allen <ioplex@gmail.com> - 2025-03-07 08:20 -0500

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